code: def _average_linkage(*args, **kwargs):
      kwargs["linkage"] = "average"
      return linkage_tree(*args, **kwargs)
  
imports: from heapq import heapify, heappop, heappush, heappushpop
  import warnings
  import numpy
  from scipy import sparse
  from ..base import BaseEstimator, ClusterMixin
  from ..externals.joblib import Memory
  from ..externals import six
  from ..metrics.pairwise import paired_distances, pairwise_distances
  from ..utils import check_array
  from ..utils.sparsetools import connected_components
  from .None import _hierarchical
  from ._feature_agglomeration import AgglomerationTransform
  from ..utils.fast_dict import IntFloatDict
  from ..externals.six.moves import xrange
label_desc: Use image node_id 5 for calling a global function with example usage: _average_linkage() and returns: linkage_tree